Helicopter transmissions branch drive outputs of one to three drive machines at torque reductions to various outputs, such as main rotor, tail rotor and auxiliary outputs. These specifically highly stressed transmissions are constructed small and light in accordance with the demands in air travel. The transmission housings are chiefly made of aluminum and magnesium alloys. The elasticity modules of these materials lie at one half to one third of the elasticity module of steel alloys. That is, the elastic deformations lie correspondingly higher under load. In particular, a twisting of the transmission housing occurs about the rotor shaft axis.
As a consequence, inputs and outputs that are arranged at a radial distance from the rotor shaft axis on the transmission shift out of their original position. Distortions and radial shifts occur on the axes of the inputs and outputs of the transmissions in relation to the axes of connectable shafts which lead to the drive machines or to the tail rotor output.
A portion of the shifts is equalized by torsionally rigid, angularly mobile disc or membrane clutches. A considerable portion of the shifts is nonetheless equalized by the as a rule very long connection shaft to the drive machines or to the tail rotor output.
For testing a helicopter transmission on a testing stand, the installation situation of the helicopter transmission in the helicopter airframe is largely simulated. Nonetheless, basically shorter drive and output shafts are used in testing stand construction for reasons of space. A greater part of the shifts must be equalized by the clutch elements owing to the shorter shafts. In addition to a basically higher load on the clutch elements due to the greater angles, essentially higher bearing stresses also occur in a radial direction on the inputs and outputs of the helicopter transmissions. The high loads at simultaneously very high rotational speeds up to approximately 25,000/min. can lead to breakage of the clutch elements and to damage in the bearing region of the input and output shafts and on the highly sensitive free wheelings of the helicopter transmissions. Very high stresses upon the components of the testing stand result from this which go beyond the operating loads in the helicopter and, in the worst case, can cause preliminary damage to the transmission.
DE 198 22 093 A1 discloses a testing stand for helicopter transmissions in which a clamping plate that can be rotated by at least one actuator about the rotor shaft axis of the test transmission is provided for accommodating the helicopter transmission. The actuators are activated in a load-dependent manner to compensate for shifts arising under load on the connection clutches of the helicopter transmission.
The clamping plate and its bearing are nonetheless relatively expensive. The invention is, therefore, based upon indicating a more economical suspension of the test transmission with which an equalization of shifting is nonetheless possible.